'\" te
.\"  Copyright 1989 AT&T
.\"  Copyright (c) 2006, Sun Microsystems, Inc.,  All Rights Reserved
.\" The contents of this file are subject to the terms of the Common Development and Distribution License (the "License").  You may not use this file except in compliance with the License.
.\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing.  See the License for the specific language governing permissions and limitations under the License.
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.TH QREPLY 9F "Jan 16, 2006"
.SH NAME
qreply \- send a message on a stream in the reverse direction
.SH SYNOPSIS
.LP
.nf
#include <sys/stream.h>



\fBvoid\fR \fBqreply\fR(\fBqueue_t *\fR\fIq\fR, \fBmblk_t *\fR\fImp\fR);
.fi

.SH INTERFACE LEVEL
.sp
.LP
Architecture independent level 1 (DDI/DKI).
.SH PARAMETERS
.sp
.ne 2
.na
\fB\fIq\fR\fR
.ad
.RS 6n
Pointer to the queue.
.RE

.sp
.ne 2
.na
\fB\fImp\fR\fR
.ad
.RS 6n
Pointer to the message to be sent in the opposite direction.
.RE

.SH DESCRIPTION
.sp
.LP
The \fBqreply()\fR function sends messages in the reverse direction of normal
flow. That is, \fBqreply(\fR\fIq\fR\fB,\fR \fImp\fR\fB)\fR is equivalent to
\fBputnext(OTHERQ(\fR\fIq\fR\fB),\fR \fImp\fR\fB)\fR.
.SH CONTEXT
.sp
.LP
The \fBqreply()\fR function can be called from user, interrupt, or kernel
context.
.SH EXAMPLES
.LP
\fBExample 1 \fRCanonical Flushing Code for STREAMS Drivers.
.sp
.LP
This example depicts the canonical flushing code for STREAMS drivers. Assume
that the driver has service procedures so that there may be messages on its
queues. See \fBsrv\fR(9E). Its write-side put procedure handles \fBM_FLUSH\fR
messages by first checking the \fBFLUSHW\fR bit  in the first byte of the
message, then the write queue is flushed (line 8) and the \fBFLUSHW\fR bit is
turned off (line 9). See \fBput\fR(9E). If the \fBFLUSHR\fR bit is on, then the
read queue is flushed (line 12) and the message is sent back up the read side
of the stream with the \fBqreply()\fR function (line 13). If the \fBFLUSHR\fR
bit is off, then the message is freed (line 15). See the example for
\fBflushq\fR(9F) for the canonical flushing code for modules.

.sp
.in +2
.nf
1  xxxwput(q, mp)
 2    queue_t *q;
 3    mblk_t *mp;
 4  {
 5	    switch(mp->b_datap->db_type) {
 6	    case M_FLUSH:
 7           if (*mp->b_rptr & FLUSHW) {
 8                  flushq(q, FLUSHALL);
 9                  *mp->b_rptr &= ~FLUSHW;
10	          }
11           if (*mp->b_rptr & FLUSHR) {
12                  flushq(RD(q), FLUSHALL);
13	                 qreply(q, mp);
14           } else {
15	                 freemsg(mp);
16	          }
17           break;
	      ...
18     }
19  }
.fi
.in -2

.SH SEE ALSO
.sp
.LP
.BR put (9E),
.BR srv (9E),
.BR OTHERQ (9F),
.BR flushq (9F),
.BR putnext (9F)
.sp
.LP
\fIWriting Device Drivers\fR
.sp
.LP
\fISTREAMS Programming Guide\fR
